Prime Minister Scott Morrison announces an unprecedented $130 billion wage subsidy scheme in March, promising it will help save six million jobs.

It is rolled out at high speed, hitting millions of workers’ bank accounts in May and reaching the “target” of six million workers covered last week.

Then on Friday May 22, Treasury announces a big surprise.

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It turns out that demand for the JobKeeper scheme is exactly half what was expected. As cock-ups go, it was an accounting error for the ages.

Good news: the scheme will only cost $70 billion.

Bad news? Only three million workers are getting paid the $1500 a fortnight wage subsidy.

That’s a $60 billion stuff up. It’s also $60 billion less cash stimulus hitting the economy just as Australia enters into a recession.

Treasury had claimed that without JobKeeper the unemployment rate would be 15 per cent, not the 10 per cent forecast.

So what happens now?

As Labor’s treasury spokesman Jim Chalmers observed: “For weeks the Morrison government has been telling casuals and other excluded workers that the JobKeeper program was full when in reality it was three million workers short.”

“If they can’t get this basic maths right how can we expect them to get the recovery right?’’ he said.

Of course, the maths jibe is pure politics.

Treasury officials and economists are not psychics, even if some of their predictions suggest you would be better off calling an astrologer for an economic forecast.

Forecasting how many companies would apply for JobKeeper in the middle of a pandemic is not easy.

Remember, Treasury came up with the six million jobs figure in March, when it was expected the states might embrace even tougher lockdowns including shutting down construction sites.

Getting it out by three million workers and $60 billion though? That does seem impressive.

Still, it’s a good problem to have because, despite the brief sting of humiliation, there’s a long term benefit to the federal budget.

Treasurer Josh Frydenberg and taxpayers basically just got hit in the arse by a rainbow - to steal Paul Keating’s famous line - because that’s $60 billion Australia will no longer need to borrow and spend decades paying back.

However, there are a few things about Treasurer Josh Frydenberg’s story that do not add up.

Let’s start with the claim that the fiasco was sparked by employers filling out a “confusing” form, because if you believe that, you believe anything.

The Treasurer was informed of the $60 billion stuff up on Thursday night by the Australian Tax Office (ATO).

The ATO told the Treasurer that a reporting error in the estimates of the number of employees likely to access the JobKeeper program was to blame.

The most common error was inflating the number of employees they expected to be eligible.

For example, instead of putting a ‘1’ in the form they put the 1500 - the amount of JobKeeper they expected to secure.

But this is an excuse for not spotting the error earlier.

It’s not an explanation for why Treasury did not correctly forecast how many workers would be eligible for JobKeeper in the first place.

Remember, weeks before the Australian Tax Office ever devised the “confusing form”, the Prime Minister said the scheme would cost $130 billion and help six million workers.

The “confusing” form had nothing to do with the original prediction.

Treasury is still conducting a review of the JobKeeper scheme that will be concluded in June.

The discovery of the $60 billion accounting error will not fill the Morrison Government with confidence about its findings.

It will increase the pressure on the PM to extend the scheme to more casuals and even Australian workers working for overseas companies.

However, the PM has offered little indication he is enthused by that idea. The Treasurer has forecast no “wholesale changes” only adjustments.